The semiconductor integrated circuit (IC) industry has experienced rapid growth. A conventional semiconductor manufacturing process involves processing one or more wafer lots, each wafer lot including one or more wafers. The wafers are eventually cut into a plurality of die, and each die contains a complete IC device. The IC devices of a wafer lot often exhibit varying IC characteristics, which can be classified into various bin categories (i.e., BIN 1, BIN 2, BIN 3, . . . etc.). For example, IC devices classified as BIN 1 (i.e., bin category 1) may have higher speed and are thus regarded as one category, while IC devices classified as BIN 7 (i.e., bin category 7) may have a lower leakage current and are therefore regarded as another category. Other bin categories may be defined according to various electric parameters and/or parameter ranges. The bin categories may be associated with various yields.
Each wafer lot may be characterized by a bin ratio, which represents the ratio (or percentage) of the lot exhibiting IC characteristics associated with each bin category. For example, if there are three bin categories, the bin ratio (BIN 1:BIN 2:BIN 3) of a wafer lot may be 2:1:1. In other words, 50% of the die in the wafer lot will exhibit IC characteristics associated with BIN 1, 25% of the die in the wafer lot will exhibit IC characteristics associated with BIN 2, and 25% of the die in the wafer lot will exhibit IC characteristics associated with BIN 3. A customer often specifies particular IC characteristics when ordering IC devices, thus a customer's order is associated with one or more bin categories. Conventional bin ratio forecasting systems and methodology exhibit a larger than desirable prediction error and lacks the ability to predict a bin ratio for a wafer lot at an earlier stage. Thus, it is desirable to be able to predict the bin ratio for wafer lots that will be processed based on the customer's order at an earlier stage and control the bin ratio.
Accordingly, what is needed is a method and system that addresses the above stated issues.